Thermo Scientific Dionex ICS-5000, Operator'S Manual

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Dionex ICS-5000 Operator’s Manual
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Doc. 065342-06 12/11
8.28.5 Leak in pH-Ag/AgCl Reference Electrode Compartment
•
Defective pH-Ag/AgCl reference electrode O-ring
Replace the pH-Ag/AgCl reference electrode O-ring (see Section 9.28.7 ).
8.28.6 Shift in Ag/AgCl Reference Potential
•
Faulty pH-Ag/AgCl reference electrode
A shift in reference potential causes a shift in the effective potential
applied to the working electrode. For example, when using an electrode
with a shift of 50 mV, an applied potential of 0.1 V, is equivalent to an
applied potential of 0.15 V for a new pH-Ag/AgCl reference electrode
with no shift.
Following the steps below, measure the pH-Ag/AgCl reference electrode
potential shift by comparing it to the potential shift of an unexposed
electrode. A spare pH-Ag/AgCl reference electrode (P/N 061879) stored
in 3 M KCl can be kept on hand for this purpose.
Using a Digital Voltmeter to Determine Reference Potential Shift
1. For each pH-Ag/AgCl reference electrode (the unexposed electrode and
the electrode being tested), use a straightened paper clip or short piece of
wire of a suitable diameter to connect the voltmeter’s voltage inputs to
pin 1 on the reference electrode’s cable connector.
To identify the cable connector pins, refer to Product Information Update
for the Electrochemical Detector (PIU_ED_1). The document is included
on the Thermo Scientific Reference Library DVD (P/N 053891).
2. Immerse both electrodes in a solution of 0.1 M KCl.
3. Read the potential difference (in mV) between the unexposed electrode
and the electrode being tested. If it is greater than 30 mV, try regenerating
the electrode by soaking it in a solution containing 1 M KCl and 1 M HCl.
If this does not reduce the potential shift, replace the electrode (see
Section 9.28.7 ).